Isomerization process



United States Patent ice 3,235,618 ISOMERIZATION PROCESS John Happel, Hastings on Hudson, Charles J. Marsel,

Flushing, and Joachim H. Blanck, Bronx, N.Y., assignors, by mesne assignments, to National Lead Company,

New York, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 2, 1962, Ser. No. 227,714 9 Claims. (Cl. 260-678) This invention relates to a process for the vapor phase isomerization of allene to methyl acetylene.

In the following specification the term conversion is intended to refer to the number of moles of allene reacted per mole of allene fed, the term selectivity to the moles of methyl acetylene produced per mole of allene reacted, and the term yield to the moles of methyl acetylene produced per mole of allene fed.

It is known to isomerize allene to methyl acetylene by contacting the former in the vapor phase and at elevated temperature with a silica-alumina catalyst activated with fluorine, hydrogen fluoride or other inorganic fluoride. This procedure is subject to the difficulties inherent in handling the various toxic and corrosive fluoride materials including HF.

It is among the objects of the present invention to provide a relatively simple process for isomerizing allene to methylacetylene which provides improved yields of methyl acetylene product, which secures increased catalyst life and which does not necessitate the use of highly corrosive and toxic catalyst activators.

Other objects and advantages of the present invention will be apparent from the following detailed description thereof.

In accordance with the invention, a process for the isomerization of allene to methyl acetylene is provided, which involves contacting allene in the vapor phase at a temperature of from about 150 to 410 C. with an alumina catalyst activated with a halocarbon activator having the formula C H HAL -F wherein HAL is a halogen radical, n is an integer from one to four, x is an integer from zero to nine, y is an integer from zero to nine and z is an integer from one to ten. The halogen radical may be either chlorine, bromine or iodine.

The activated alumina catalyst employed in the isomerization process is prepared by contacting an alumina catalyst with the aforesaid halocarbon at a temperature sufficiently high to cause the halocarbon to decompose on contacting the alumina catalyst particles. In this manner an activated isomerization catalyst is produced having a relatively long catalyst life, which may be readily reactivated by further treatment with the halocarbon activator. Moreover, the use of the thus resulting activated catalyst provides relatively high yields of the methyl acetylene and conversions of the allene reacted.

The alumina catalyst to be activated need not be a specially prepared or highly purified activated alumina. It has been found that commercially available activated aluminas provide highly active catalysts for allene isomerization.

Preferred halocarbon activators include fluoroform, tetrafiuoromethane, dichlorodifluoromethane, bromotrifluorornethane, chlorodifluoromethane, 1,2-dichlorotetrafiuoroethane and bromotrifluoroethane. While the activating temperature required to decompose the halocarbon employed depends upon the particular halocarbon, it has been found that, employing the above compounds, activating temperatures of from about 350 to about 850 C. are suitable. The activation treatment is preferably continued until free chlorine, bromine or iodine is recovered from the gaseous eflluent from the activation reaction mixture, although shorter activating periods can 3,235,618 Patented Feb. 15, 1966 produce catalysts having sufficiently high isomerization activities. It has been found that generally from about 1 to 20 minutes are required to effect activation of alumina catalysts with the above typical halocarbon activators at the indicated activation temperatures.

Preferably, a catalyst chamber is initially loaded with granular or pelleted alumina admixed with an inert, heat stabilizing material such as quartz. Other inert, solid diluents which may be used in place of quartz include, for example, porcelain, corundum, and the like. In the absence of an inert diluent, undesirable cracking of the hydrocarbon feed tends to occur. The catalyst is then activated by passing the aforesaid halocarbon activator over it at a temperature sufiicient to decompose the halocarbon. The activator is admitted, in the case of gases, under its own cylinder pressure, either alone or diluted with an inert gas such as nitrogen. Liquid activators are admitted to the catalyst chamber by bubbling an inert gas through them, the resulting vapor mixture being carried into contact with the heated alumina catalyst.

A similar technique is employed to reactivate an alumina catalyst after it has become deactivated through extended or improper use. The reactivation is carried out as a separate cycle in the manner described above, or it may be part of a regeneration cycle during which air or other oxidizing vapor is fed into the catalyst chamber to decarbonize the catalyst. When reactivated in the latter manner, the halocarbon activator is fed to the catalyst chamber alone, or in admixture with the regenerating gases, the temperature of regeneration usually being sufficient to elfect decomposition of the halocarbon in the presence of the alumina catalyst. If necessary, heat is added to effect decomposition of the activator.

The isomerization may be carried out with a feed stock of pure allene or with a feed stock containing allene in addition to other low molecular weight hydrocarbons, such as may be present in reaction mixtures formed during the production of allene. The activated catalyst, prepared as described above, is contacted with the vaporous feed stock at a temperature of from about 150 to about 410 C. It has been found that, when the isomerization is carried out at temperatures below about 150 C., relatively little conversion of the allene occurs, whereas when temperatures above about 410 C. are employed, the conversion is substantially complete but results in the production of contaminated end products. Preferably, the isomerization reaction is carried out at temperatures of from about 200 to about 400 C., at which the most satisfactory results have been obtained. The isomerization is ordinarily carried out at about atmospheric pressure.

The gaseous isomerization mixture is caused to flow over the catalyst at a space velocity preferably ranging from about 50 volumes of vapor flowed per hour per volume of catalyst space, to about 1000 volumes of vapor flowed per hour per volume of catalyst space, measured at S.T.P. (0 C., one atmosphere pressure). The space velocities utilized vary directly with the temperature of the reaction, the higher space velocities within the indicated range being employed at the higher isomerization reaction temperatures.

The following examples illustrate specific embodiments of the allene isomerization process of the present invention; it will he understood the examples are given for illustrative purposes and that the invention is not limited thereto.

A mixture of equal parts, by volume, 42.4 grams of activated alumina granules (commercial grade Fl0 Aluminum Corp. of America) and 68.9 grams quartz chips was prepared in each of the following examples. cc. of each mixture thus produced was loaded into a catalyst chamber and heated to a temperature suflicient to decompose the halocarbon activator thereafter added thereto. Gaseous activators were fed to the catalyst chamber under their own pressures, and liquid activators were fed in nitrogen streams bubbled therethrough. The

When the space velocity was decreased to 165 volumes per volume per hour and the reaction was carried out at the same temperature, the conversion of allene was 20.8% and the selectivity and yield of methyl acetylene were 82.0% and 17.1%, respectively.

activating procedure was carried out for a 10 minute 5 1 period at atmospheric pressure. Examp e XI Thereafter, allene was passed over the resulting acti- An activated catalyst similar to that employed in Examvated catalyst at atmospheric pressure and methyl acetyple I above was utilized to isomerize an allene-hydrocarlene thereby produced. The following table identlfies l bon mixture containing the following components: the activated catalyst employed, the temperature of Com Onent Mole er ant the activation, the isomerization reaction conditions and g p 8 the production of methyl acetylene therefrom in each 31116 of a series of runs. mpy ene Example I i II I III IV V VI Catalyst Activator CC12F2 CHClF-g 0,0121% CF4 CHFa CzHzBrFs Activation Temperature,

0-, 460 565 560 595 650 600 Isomerization Temperar ure, C 280 350 345 325 355 365 Space Velocity (Volume of vapor flowed per hour per volume of catalyst space) 165 165 165 165 165 155 Percent conversion 47. 8 81. 1 78 2 79. 2 80.1 77. 7 Percent selectivity 84, 8 82. 7 78. 2 83. 1 7. 2 9L 4 Percent; yield 40. 67. 1 61. 2 65. 3 69. 8 71. 0

Example VII Allene 40.6

The activated catalyst prepared in Example I above fi g acetylene 209 was reactivated after a number of isomerization cycles in i we the following manner. 5

After regeneration with nitrogen and air to burn ofi so mane the carbonaceous deposit formed on the catalyst additional dichlorodifiuoromethane was admitted to the catalyst the reaction was fi out at a temperature chamber under the same conditions employed during the of 280 and the Vapor mlxmre was Passad Over the initial activation. Upon repeating the allene isomerizacatalyst at a rate of volumes P Volume of catalyst tion at a temperature of 280 C. and a space velocity of Per Pq the cI}veTs1On of allene was 443%: and the 165 volumes of vapor per hour Per volume of catalyst 40 selectivity and yield of methyl acetylene were 83.9% space, 5 8.4% of the allene was reacted, and the selectivity and 371% F Y- and yield of methyl acetylene were 94.3% and 55%, re- The lfresent mvenn'on P a Process for spective1y isomerizing allene, which provides relatively high yields Example VH1 if rcrlilethyl facetylene, and which process does not entail an in o toxic or corr A catalyst similar to the catalyst employed in Example certain 'i may be 822: s igg g izg gigi 3 f P 87 :i 1% f i out departing from the scope of the invention, it is int t gg 'i z O an t 0 5 S a tended that all matter contained in the above description g gggz g g g gig Z3 53: g f y at shall be interpreted as illustrative and not in a limiting sense. temperature of 380 C. employing a space velocity of What is Claimed is 165 volumes of vapor flow per hour per volume of 1 A r f h catalyst space, the allene was 83.5% reacted, and methyi 1 p oce.ss or e .ISOmeHZaUPH of aHenF to met yl acetylene was produced with a selectivity of 70.7% and acety which comprises contacting allene In the .vapor a yield of 59% phase at a temperature of from 150- to 410 C. with an Example IX alumnia catalyst activated by decomposing a halocarbon ving the formula C H I-lAL F wherein HAL is a a temperature of 210, employing a space velocity of 165 tegcrdfrqm i to y IS an Integer from mm volumes of vapor flow per hour per volume of catalyst O i an anmteger from one to m the Presence space; under these isomerization conditions the allene 6O f catalyst was 20.8% reacted and methyl acetylene was produced e Process a i clalm Whlch the with a Selectivity of 82.0% and a yidd of 111% isomerization reaction 15 carried out at a temperature When the isomer-ization reaction temperature was inof from 2000 to 9 the rfiactioll Vapors are creased to 430 C., the allene was 100% reacted but flowed over the acm'atad wmlyst at a Space Velocity the selectivity and yield of methyl acetylene were negli- 0 from 50 to 1,000 Volumes of Vapor P hour P ibl volume of catalyst space.

Example X 3. The process as defined in claim 1, in which said An activated catalyst Similar to that employed in halocarbon activator is a compound selected from the Example I above was utilized to isomerize allene at a group cfmslstmg of fiuoroform tetmflueromethane, temperature of c" employing a space velocity of chlorodifiuoromethane, brornotrifluoromethane, chlorodi- 325 Volumes of vapor flow Per per Volume f fluoromethane, 1,Z-dichlorotetrafiuoroethane and bromocatalyst; under such conditions the allene was 13.5% TflfluOfOethanereacted and methyl acetylene was produced with a 4. The Process as daim 1, in which S id haloselectivity of 85.7% and a yield of 11.7%. carbon is fluoroforrn.

5. The process as defined in claim 1, in which said halocarbon is tetrafluoromethane.

6. The process as defined in claim 1, in which said halocarbon is bromotrtifluoroethane.

7. The process as defined in claim 1, in which said halocarbon is 1,2-dichlorotetrafiuoroethane.

8. The process as defined in claim 1, in which said halocarbon is chlorodifluoromethane.

9. In a cyclic vapor phase process for the isomerization of allene to methyl acetylene which comprises the steps of contacting allene in the vapor phase at a temperature of from 150 to 410" C. With an activated alumina catalyst, regenerating the alumina catalyst to remove carbonaceous material therefrom and periodical- 1y reactivating sa-id catalyst, the improvement which comprises activating and reactivating the alumina catalyst by decomposing a halocarbon having the formula 5 perature of from 350 to 850 C.

References Cited by the Examiner UNITED STATES PATENTS 2,594,706 4/1952 Allan 260678 FOREIGN PATENTS 1,299,388 6/1962 France.

ALPHONSO D. SULLIVAN, Primary Examiner. 

1. A PROCESS FOR THE ISOMERIZATION OF ALLENE TO METHYL ACETYLENE, WHICH COMPRISES CONTACTING ALLENE IN THE VAPOR PHASE AT A TEMPERATURE OF FROM 150* TO 410*C. WITH AN ALUMNIA CATALYST ACTIVATED BY DECOMPOSING A HALOCARBON HAVING THE FORMULA CNHXHALYFZ, WHEREIN HAL IS A HALOGEN RADICAL, N IS AN INTEGER FROM ONE TO FOUR, X IS ANTEGER FROM ZERO TO NINE, Y IS AN INTEGER FROM ZERO TO NINE AND Z IS AN INTEGER FROM ONE TO TEN, IN THE PRESENCE OF SAID ALUMINA CATALYST. 